> However, it doesn't appear that the suspend
> and resume on lid close, etc. work in this
> case (presumably because the USB subsystem
> must remain powered to run the SD interface).
>> Is there any possibility of enabling support for
> power management *even if* the system OS is
> booting from an SD card?
USB is not involved in the SD card. But there are some bugs in how
the SD interface chip is re-initialized on resume. This tends to
crash the kernel when either root or swap is on the SD card. See
http://dev.laptop.org/ticket/5923
"Suspend loses / if booted from SD" -- incorrectly closed as "duplicate"
(but never states which bug it dups)
http://dev.laptop.org/ticket/6532
"SD card corruption" -- incorrectly closed since not fixed in a release.
http://dev.laptop.org/ticket/1339
"CAFE SD controller doesn't wake up fast enough" (still open -- and
probably needs a look from Pierre Ossman: Mitch has probably
found the hardware glitch that was bugging you!)
There are more, read those for pointers.
Suspend/resume while booted from SD is certainly possible in hardware,
but we've been stumbling around in a world of broken software for
years, and haven't yet made all the required fixes. As the XO ages
and its flash memory looks smaller and smaller, SD card fixes will
gradually get higher and higher priority.
John